Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Pedogenesis and Hydromorphology of Soils in Mid-Atlantic Barrier Island Landscapes(2014) Rossi, Ann Marie; Rabenhorst, Martin C.; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Barrier islands are an important and dynamic component of coastal ecosystems. While a number of studies have focused on the geomorphology, landform dynamics, vegetation patterns, and ecology of barrier islands, there has been relatively little attention paid to the soils, which are an important ecosystem component. The goal of this study was to improve our understanding of the processes and factors influencing soil development on Mid-Atlantic barrier islands. The study was conducted at Assateague Island National Seashore, a barrier island located on the eastern coast of Maryland and Virginia. Study sites ranged in relative surface stability (soil age) and topography, allowing for comparison of the influence of time and soil moisture on pedogenic processes. Soil development was limited because of the young age of the soils and weathering resistant parent material. Evidence of pedogenesis was reflected primarily in accumulations of organic matter and formation of A and O horizons. Carbon accumulation was controlled by the magnitude of carbon inputs (plant biomass), which increased with soil age and wetness, and by decomposition, which was regulated by soil saturation and anaerobiosis. On a global scale, average soil carbon stocks in these soils tend to be low, due to their young age and the environmental stresses faced by plants in these environments (which limits organic inputs). However, relatively high total carbon stocks were documented on the older, forested parts of the island. Soil wetness also affected the development of subsoil horizons. Weak Bw horizons, with brighter chromas and redder hues, were described in relatively well drained, oxidized soils due to slight accumulations of iron (hydro)oxides and organic matter. In poorly and very poorly drained soils iron was reduced, precluding the formation of Bw horizons. Reduced subsoil horizons had low chroma matrix colors. Despite meeting the requirements for hydric soils, many of the wet barrier island soils do not have morphologies typical of hydric soils. Nevertheless, the low chroma colors and organic accumulations at the surface (Oa horizon) proved to be a reliable indicator of soil wetness and became the basis for a proposed set of hydric soil field indicators for Mid-Atlantic barrier islands.Item HYDROMORPHOLOGY OF ANOMALOUS BRIGHT LOAMY SOILS ON THE MID-ATLANTIC COASTAL PLAIN(2009) Zurheide, Philip Klaus; Rabenhorst, Martin C; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Some loamy textured soils along the Mid-Atlantic coastal plain undergo extended periods of saturation or ponding, yet lack the hydromorphology that identifies them as hydric by any of the currently approved Field Indicators of Hydric Soils (FI). Termed Anomalous Bright Loamy Soils (ABLS), these were identified at four research sites on the Delmarva Peninsula. The hydrologic and biogeochemical status of these soils was monitored for three years along a hydrosequence at each site. A series of field and lab experiments were run to investigate the possible causes for the ABLS-phenomenon. The most likely cause is a combination of low hydrologic gradient coupled with the length of time since saturation. Using observed morphology, a newly developed Field Indicator successfully discriminated between five hydric soils that lacked an approved indicator and those that were not hydric. This indicator has now been approved as an official FI of Hydric Soils (F20).Item Hydrologic and Biogeochemical Storm Response in Choptank Basin Headwaters(2008) Koskelo, Antti; Fisher, Thomas R; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study quantified the effect of hydric soils on the hydrology and biogeochemistry of sub-watersheds across the Delmarva Peninsula. For hydrology, long-term data were compiled for 13 United States Geological Survey sites and evaluated for hydric soil effects. Results show that hydric soils reduce baseflow by increasing ponding and subsurface water storage, resulting in greater evapotranspiration. In contrast, hydric soils were unrelated to stormflow, which was instead driven by topography. During hourly sampling of 18 storms in the Choptank Basin, most forms of nitrogen and phosphorus increased in concentration due to erosion and re-suspension of sediments. Nitrate, however, decreased during storms due to dilution of nitrate-rich groundwater by runoff. Baseflow nitrate concentrations decreased with forested hydric soils, likely due to greater denitrification in forested hydric areas. Annually, much of the total nitrogen and phosphorus export occurred during storms, emphasizing the need to sample a wide range of flows to improve estimates of nutrient losses.